According to an informal survey cited by the American Society for health care Engineering, about one-quarter of all hospitals ban cellphones entirely, half ban them from patient care areas, and the remaining quarter have no ban.

The bans go back to early reports from the 1980s that turning on a cellphone could turn off a ventilator or disrupt monitoring equipment.

But in surveying the engineering and medical literature on the topic, the researchers found that most incidents were single-case reports rather than widespread problems.

Modern digital cellphones use much less power than older analog models. And in 1979, the Food and Drug Administration created guidelines for shielding electronic medical devices, the paper notes.

By 1999, the Emergency Care Research Institute, a prominent private hospital advisory group, had updated its recommendations to allow the use of cellphones when quick clinical communication was needed.